GB2252413A

GB2252413A - Electrode for electromagnetic flowmeter

Info

Publication number: GB2252413A
Application number: GB9201044A
Authority: GB
Inventors: Johann Lemmerer
Original assignee: Krohne AG
Current assignee: Krohne AG
Priority date: 1991-02-04
Filing date: 1992-01-17
Publication date: 1992-08-05
Also published as: DE4139915A1; GB9201044D0

Abstract

An electromagnetic flowmeter 30 has electrodes 10 which include a body 12 which is of a non-metallic, flexible, electrically conductive material. The material is preferably an elastomer, and particularly natural rubber, incorporating carbon black, and has a Shore Hardness of 100 or less. Preferably a pair of electrodes are mounted on opposed sides of the flow tube 32 of the flowmeter. The flow tube may be lined with an elastomer 34, particularly a rubber material, with the electrode projecting through a hole 40 in the lining and terminating flush with the lining where they are retained by an adhesive material. The other end of the electrode may be retained in a housing 36 by epoxy resin bonding compound 42. <IMAGE>

Description

2 2 -S -- z, 1 - 1 41 A MWMETER 11 THIS INVENTION relates to a flowmeter.

More particularly, the invention relates to an electrode for a flowmeter and to a flowmeter including such electrode.

According to a first aspect of the invention, there is provided an electrode for a flowmeter, the electrode including a body which is of a non-metallic, flexible, electrically conductive material.

Preferably, the body of the electrode is of a material which has a Shore Hardness of less than 100. More specifically, the body of the electrode m. ay have a Shore Hardness similar to that of rubber. In otherwords, the body of the electrode may have a Shore Hardness of approximately 50 and an electrical resistance of less than 1000 Q/cm 3 2 The material from which the body is made may be a compound comprising a mixture of an elastomeric material and carbon black. The elastomeric material may be a natural rubber material.

The compound may comprise a mixture of approximately 20% to 30% carbon black and 70% to 80% natural rubber. 1 The electrode may be in rod form having a circular cylindrical cross- section.

According to a second aspect of the invention, there is provided a flowmeter which includes a flow tube mountable co-axially within a material carrying conduit; a pair of electrodes, as described above, mounted on opposed sides of the flow tube to be in communication with an interior of the flow tube; and a signal processing means to which the electrodes are connected.

An interior of the flow tube may be lined with lining of an elastomeric material. The lining may be rubber material.

Each electrode may project through an opening in the lining, so that an end of the electrode lies ,I L, ' 3 substantially flush with an interior surface of the lining. The openings in the lining may be shaped and dimensioned so that the ele ctrodes are each a snug fit therein.

the li The electrodes may be retained in position 1 ning by means of an adhesive material.

An opposed end of each electrode may be contained in an electrode cas4Ang and may be retained in position by a bonding compound contained within the casing.

The bonding compound may comprise an epoxy resin and hardener blend. The epoxy resin and the hardener may be present in a ratio of approximately 7 5: 2 5.

The epoxy resin may be a medium viscosity resin. Preferably, the resin is an unmodified liquid bisphenol A-epichlorohydrin epoxide resin.

The hardener may be a viscous liquid amino polyamide hardener.

A cap member may be securable to each electrode casing for retaining and locating the electrode within its casing.

4 The f low tube may carry an electromagnetic f ield inducing means thereon. The electromagnetic f ield inducing means may be in the form of at least one coil.

The invention is now described by way of example with reference to the accompanying diagrammatic drawings.

In the drawings, Figure 1 shows a sectional axial view of an electrode, in accordance with a first aspect of the invention, for a flowmeter; Figure 2 shows a sectional view of part of a flowmeter in accordance with a second aspect of the invention, including the electrode of Figure 1; Figure 3 shows a part sectional side view of a flow tube of the flowmeter of Figure 2; and Figure 4 shows a part sectional front view of a flow tube of the flowmeter of Figure 3.

Referring firstly to Figure 1 of the drawings, an electrode, in accordance with the invention, is illustrated and is designated generally by the reference numeral 10.

The electrode 10 comprises an elongate rod-like body member of a nonmetallic, flexible, electrically conductive material. The material from which the body is made has a Shore Hardness of 1., approximately 50 and an approximately goo U/CM3.

electrical resistance of The material from which the body 12 is made is a compound comprising a mixture of an elastomeric material, in the form of natural rubber and carbon black. Preferably, the compound comprises a mixture of approximately 25% carbon black to 75% natural rubber to provide the required flexibility and the electrical conductivity.

An electrode cable 14 is connected to the body 12 via a plug 16. The cable 14 has a spigot-like member 18 secured to an end thereof which is soft-soldered in a corresponding socket 20 defined in the plug 16.

Referring now to Figures 2 and 3 of the drawings, a flowmeter, in accordance with a second aspect of the invention is illustrated and is designated generally by the reference numeral 30.

The flowmeter 30 comprises a flow tube 32 which, in use, is mounted coaxially in a _materials carrying conduit (not shown).

An inner surface of the flow tube 32 is lined with a lining 34 of an elastomeric material such as rubber.

6 A pair of electrode casings 36 (one of which is shown in Figures 2 and 3 of the drawings) is secured to the flow tube 32, the electrode casings 36 being arranged on opposed sides of the flow tube 32. Each electrode casing 36 surrounds an opening 38 defined in the wall of the flow tube 32.

An opening 40 is also def ined in the lining in which the body 12 of the electrode 10 is a snug fit. The body 12 of the electrode 10 is retained in position in the lining 34 by means of a suitable adhesive material such as that known by the trade name Eurecryl 2456 supplied by Chempro of Wadeville, Germiston, Transvaal Province, Republic of South Africa. The end of the body 12 of the electrode 10 located within the lining 34 lies substantially flush with an interior surface of the lining 34.

For retaining the electrode 10 in position in its electrode casing 36, a chamber 42 defined by the casing is substantially filled with a bonding compound 44. The bonding compound 44 comprises an epoxy resin and hardener blend. The epoxy resin and the hardener are present in a ratio of approximately 75:25.

The epoxy resin is a medium viscosity resin such as, for example, an unmodified liquid bisphenol Aepichlorohydrin epoxide resin. The hardener 4.s a 7 viscous liquid amino polyamide hardener.

The Applicant believes that a bonding compound of these materials will provide the required flexibility and bonding capabilities.

once the cavity 42 has been f illed with the bonding compound 44, a washer 46 of a PTFE material is mounted about the cable and a screw cap 48 is screwed to the electrode casing 36.

The flow tube 32 also supports an electromagnetic field inducing means in the form of coils. The coils (not shown) are secured by coil plates 50 and coil bolts 52 as shown in Figure 4.

The electrodes 10 are then connected to signal processing circuitry (not shown) for use of the flowmeter 30. The signal processing circuitry is in the form of conventional circuitry which will be known to persons skilled in the art. As such, the signal processing circuitry is not described any further herein.

It is a problem with conventional flowmeters, in the measurement of flow rates of slurries, for example in mines, that due to the abrasive nature of the c 8 slurries, a tribo-effect is induced. This causes noise to be generated resulting in spurious measurements by the electrodes.

It has previously been proposed to recess the electrodes with respect to an inner surface of a lining of the flow tube in order to overcome the tribo-effect. However/ the measurements obtained by recessed electrodes do not always provide the requisite degree of accuracy.

The Applicants believe that with the provision of electrodes 10 in accordance with the invention, more accurate readings in the measurement of flow rates of slurries can be obtained than has heretofore been possible. Further, the Applicants believe that the electrodes 10, being of a soft material, will be able to withstand impacts by the slurries being transported.

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Claims

CLAIMS:

An electrode for use with a flowmeter, the electrode including a body which is of a non-metallic, flexible. electrically conductive material.
2. An electrode as defined in Claim 1, wherein the body of the electrode is of a material which has a Shore Hardness of 100 or less.
3. An electrode as def ined in Claim 1 or 2, wherein the body of the electrode is of a material which has a Shore Hardness of approximhtely 50 and an electrical resistance of less than 1000 ohms/ CM3.
4. An electrode as defined in any of the above Claims, wherein the body is made from a compound comprising a mixture of an elastomeric material and carbon black.
5. An electrode as defined in Claim 4, wherein the elastomeric material is a natural rubber material.
6. An electrode as defined in Claim 5, wherein the compound comprises a mixture of approximately 20% to 30% carbon black and 70% to 80% natural rubber.
7. An electrode as defined in any of the above Claims, wherein the electrode is in a rod form having a circular cross-section.
8. A flowmeter which includes: a flow tube mountable coaxially within a material-carrying conduit; a pair of electrodes, the electrodes each including a body which is of a non-metallic, flexible, electrically conductive material, mounted on opposed sides of the flow tube to be in communication with an interior of the flow tube; and a signal processing means to which the electrodes are electrically connected.
9. A f lowmeter according to Claim 8, wherein each electrode is of a material which has a Shore Hardness of 100 or less.
10. A flowmeter according to Claim 8 or 9, wherein the body of the electrode is of a material which has a Shore Hardness of approximately 50 and an electrical resistance of less than 1000 ohms/cm3.
11. A flowmeter according to Claims 8, 9 or 10, wherein the body is made from a compound comprising a mixture of an elastomeric material and carbon black.
12. A flowmeter according to Claim 11, wherein the elastomeric material is a natural rubber material.
13. A flowmeter according to Claim 12, wherein the compound comprises a mixture of approximately 20% to 30% carbon black and 70% to 80% natural rubber.
14. A f lowmeter according to any of Claims 8 to 13, wherein each electrode is in a rod form having a circular cross-section.
15. A f lowmeter as def ined in any of Claims 8 to 14, wherein the interior of the f low tube is lined with a lining of an elastomeric material.
16. A f lowmeter as def ined in Claim 9, wherein the lining is made of a rubber material.

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17. A flowmeter as defined in Claims 15 or 16, wherein each electrode projects through a respective opening in the lining, so that an end of the electrode lies substantially flush with an interior surface of the lining.
18. A flowmeter as defined in Claim 17, wherein the openings in the lining and the electrodes are shaped and dimensioned so that the electrodes are each a snug fit in the respective opening.
19. A flowmeter according to Claim 17 or 18, wherein the electrodes are retained in position in the lining by means of an adhesive material.
20. A f lowmeter according to any of Claims 8 to 19, wherein an opposed end of each electrode is contained in a casing and is retained in position by a bonding compound contained within the casing.
21. A flowmeter according to Claim 20, wherein the bonding compound comprises an epoxy resin and hardener blend.
22. A flowmeter according to Claim 21, wherein the epoxy resin and the hardener are present in a ratio of approximately 75:25.
23. A flowmeter according to Claim 21 or 22, wherein the epoxy resin is a medium viscosity resin.
24. A flowmeter according to Claims 21, 22 or 23, wherein the epoxy resin is an unmodified liquid bisphenol A-epichlarohydrin epoxide resin.

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25. A f lowmeter according to any one of Claims 21 to 24, wherein the hardener is a viscous liquid amino polyanide hardener.
26. A flowmeter according to any one of Claims 20 to 25, wherein the electrode casing is fitted with a cap member for retaining and locating the electrode within the casing.

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27. An electrode substantially as herein described with reference to the accompanying drawings.
28. A flowmeter substantially as herein described with reference to the accompanying drawings.
29. Any novel feature or combination of features disclosed herein.